Last three units now.
You can use a Cerbo/other Victron relay to turn this "on" and "off" by connecting or disconnecting the black wire loop. This can be programmed so you charge a battery from some other source, or turn some load on and off by disabling this buck-boost converter. I have paralleled up to 5 of these no problem.... but you must tune the output voltage using the screw adjust if you want to do that. Otherwise there will be a voltage mismatch and imbalance in load between converters.
Note this is NOT the same as an "Orion DC charger". This is infinitely superior from the electrical perspective. If you tune the output of this using the accessible adjust trimpot to match a battery charge voltage, it can work just like a charger.
The new "smart" ones are basically dumbed down versions of this, except with the word "smart" added to it (but they do have BT which this doesnt, this uses a hardwire from a victron relay or a manual switch). From an engineering perspective the new ones are inferior to these old ones as the old ones can be used for anything not just battery charging. Also the old ones like this can be paralleled or serialed. I paralleled 5 of these to run a kilowatt Renogy inverter from a severely mismatched battery (16.8V NMC) that would overvoltage shutdown the renogy. This is a perfect use case for these.